/* * Copyright (c) 1998, 2011, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled.hpp" #include "ci/ciMethodData.hpp" #include "compiler/compileLog.hpp" #include "libadt/vectset.hpp" #include "memory/allocation.inline.hpp" #include "opto/addnode.hpp" #include "opto/callnode.hpp" #include "opto/connode.hpp" #include "opto/divnode.hpp" #include "opto/idealGraphPrinter.hpp" #include "opto/loopnode.hpp" #include "opto/mulnode.hpp" #include "opto/rootnode.hpp" #include "opto/superword.hpp" //============================================================================= //------------------------------is_loop_iv------------------------------------- // Determine if a node is Counted loop induction variable. // The method is declared in node.hpp. const Node* Node::is_loop_iv() const { if (this->is_Phi() && !this->as_Phi()->is_copy() && this->as_Phi()->region()->is_CountedLoop() && this->as_Phi()->region()->as_CountedLoop()->phi() == this) { return this; } else { return NULL; } } //============================================================================= //------------------------------dump_spec-------------------------------------- // Dump special per-node info #ifndef PRODUCT void LoopNode::dump_spec(outputStream *st) const { if (is_inner_loop()) st->print( "inner " ); if (is_partial_peel_loop()) st->print( "partial_peel " ); if (partial_peel_has_failed()) st->print( "partial_peel_failed " ); } #endif //------------------------------is_valid_counted_loop------------------------- bool LoopNode::is_valid_counted_loop() const { if (is_CountedLoop()) { CountedLoopNode* l = as_CountedLoop(); CountedLoopEndNode* le = l->loopexit(); if (le != NULL && le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) { Node* phi = l->phi(); Node* exit = le->proj_out(0 /* false */); if (exit != NULL && exit->Opcode() == Op_IfFalse && phi != NULL && phi->is_Phi() && phi->in(LoopNode::LoopBackControl) == l->incr() && le->loopnode() == l && le->stride_is_con()) { return true; } } } return false; } //------------------------------get_early_ctrl--------------------------------- // Compute earliest legal control Node *PhaseIdealLoop::get_early_ctrl( Node *n ) { assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" ); uint i; Node *early; if( n->in(0) ) { early = n->in(0); if( !early->is_CFG() ) // Might be a non-CFG multi-def early = get_ctrl(early); // So treat input as a straight data input i = 1; } else { early = get_ctrl(n->in(1)); i = 2; } uint e_d = dom_depth(early); assert( early, "" ); for( ; i < n->req(); i++ ) { Node *cin = get_ctrl(n->in(i)); assert( cin, "" ); // Keep deepest dominator depth uint c_d = dom_depth(cin); if( c_d > e_d ) { // Deeper guy? early = cin; // Keep deepest found so far e_d = c_d; } else if( c_d == e_d && // Same depth? early != cin ) { // If not equal, must use slower algorithm // If same depth but not equal, one _must_ dominate the other // and we want the deeper (i.e., dominated) guy. Node *n1 = early; Node *n2 = cin; while( 1 ) { n1 = idom(n1); // Walk up until break cycle n2 = idom(n2); if( n1 == cin || // Walked early up to cin dom_depth(n2) < c_d ) break; // early is deeper; keep him if( n2 == early || // Walked cin up to early dom_depth(n1) < c_d ) { early = cin; // cin is deeper; keep him break; } } e_d = dom_depth(early); // Reset depth register cache } } // Return earliest legal location assert(early == find_non_split_ctrl(early), "unexpected early control"); return early; } //------------------------------set_early_ctrl--------------------------------- // Set earliest legal control void PhaseIdealLoop::set_early_ctrl( Node *n ) { Node *early = get_early_ctrl(n); // Record earliest legal location set_ctrl(n, early); } //------------------------------set_subtree_ctrl------------------------------- // set missing _ctrl entries on new nodes void PhaseIdealLoop::set_subtree_ctrl( Node *n ) { // Already set? Get out. if( _nodes[n->_idx] ) return; // Recursively set _nodes array to indicate where the Node goes uint i; for( i = 0; i < n->req(); ++i ) { Node *m = n->in(i); if( m && m != C->root() ) set_subtree_ctrl( m ); } // Fixup self set_early_ctrl( n ); } //------------------------------is_counted_loop-------------------------------- bool PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) { PhaseGVN *gvn = &_igvn; // Counted loop head must be a good RegionNode with only 3 not NULL // control input edges: Self, Entry, LoopBack. if (x->in(LoopNode::Self) == NULL || x->req() != 3) return false; Node *init_control = x->in(LoopNode::EntryControl); Node *back_control = x->in(LoopNode::LoopBackControl); if (init_control == NULL || back_control == NULL) // Partially dead return false; // Must also check for TOP when looking for a dead loop if (init_control->is_top() || back_control->is_top()) return false; // Allow funny placement of Safepoint if (back_control->Opcode() == Op_SafePoint) back_control = back_control->in(TypeFunc::Control); // Controlling test for loop Node *iftrue = back_control; uint iftrue_op = iftrue->Opcode(); if (iftrue_op != Op_IfTrue && iftrue_op != Op_IfFalse) // I have a weird back-control. Probably the loop-exit test is in // the middle of the loop and I am looking at some trailing control-flow // merge point. To fix this I would have to partially peel the loop. return false; // Obscure back-control // Get boolean guarding loop-back test Node *iff = iftrue->in(0); if (get_loop(iff) != loop || !iff->in(1)->is_Bool()) return false; BoolNode *test = iff->in(1)->as_Bool(); BoolTest::mask bt = test->_test._test; float cl_prob = iff->as_If()->_prob; if (iftrue_op == Op_IfFalse) { bt = BoolTest(bt).negate(); cl_prob = 1.0 - cl_prob; } // Get backedge compare Node *cmp = test->in(1); int cmp_op = cmp->Opcode(); if( cmp_op != Op_CmpI ) return false; // Avoid pointer & float compares // Find the trip-counter increment & limit. Limit must be loop invariant. Node *incr = cmp->in(1); Node *limit = cmp->in(2); // --------- // need 'loop()' test to tell if limit is loop invariant // --------- if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit? Node *tmp = incr; // Then reverse order into the CmpI incr = limit; limit = tmp; bt = BoolTest(bt).commute(); // And commute the exit test } if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant return false; if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant return false; Node* phi_incr = NULL; // Trip-counter increment must be commutative & associative. if (incr->is_Phi()) { if (incr->as_Phi()->region() != x || incr->req() != 3) return false; // Not simple trip counter expression phi_incr = incr; incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant return false; } Node* trunc1 = NULL; Node* trunc2 = NULL; const TypeInt* iv_trunc_t = NULL; if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) { return false; // Funny increment opcode } assert(incr->Opcode() == Op_AddI, "wrong increment code"); // Get merge point Node *xphi = incr->in(1); Node *stride = incr->in(2); if (!stride->is_Con()) { // Oops, swap these if (!xphi->is_Con()) // Is the other guy a constant? return false; // Nope, unknown stride, bail out Node *tmp = xphi; // 'incr' is commutative, so ok to swap xphi = stride; stride = tmp; } // Stride must be constant int stride_con = stride->get_int(); assert(stride_con != 0, "missed some peephole opt"); if (!xphi->is_Phi()) return false; // Too much math on the trip counter if (phi_incr != NULL && phi_incr != xphi) return false; PhiNode *phi = xphi->as_Phi(); // Phi must be of loop header; backedge must wrap to increment if (phi->region() != x) return false; if (trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr || trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1) { return false; } Node *init_trip = phi->in(LoopNode::EntryControl); // If iv trunc type is smaller than int, check for possible wrap. if (!TypeInt::INT->higher_equal(iv_trunc_t)) { assert(trunc1 != NULL, "must have found some truncation"); // Get a better type for the phi (filtered thru if's) const TypeInt* phi_ft = filtered_type(phi); // Can iv take on a value that will wrap? // // Ensure iv's limit is not within "stride" of the wrap value. // // Example for "short" type // Truncation ensures value is in the range -32768..32767 (iv_trunc_t) // If the stride is +10, then the last value of the induction // variable before the increment (phi_ft->_hi) must be // <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to // ensure no truncation occurs after the increment. if (stride_con > 0) { if (iv_trunc_t->_hi - phi_ft->_hi < stride_con || iv_trunc_t->_lo > phi_ft->_lo) { return false; // truncation may occur } } else if (stride_con < 0) { if (iv_trunc_t->_lo - phi_ft->_lo > stride_con || iv_trunc_t->_hi < phi_ft->_hi) { return false; // truncation may occur } } // No possibility of wrap so truncation can be discarded // Promote iv type to Int } else { assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int"); } // If the condition is inverted and we will be rolling // through MININT to MAXINT, then bail out. if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice! // Odd stride bt == BoolTest::ne && stride_con != 1 && stride_con != -1 || // Count down loop rolls through MAXINT (bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0 || // Count up loop rolls through MININT (bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0 ) { return false; // Bail out } const TypeInt* init_t = gvn->type(init_trip)->is_int(); const TypeInt* limit_t = gvn->type(limit)->is_int(); if (stride_con > 0) { long init_p = (long)init_t->_lo + stride_con; if (init_p > (long)max_jint || init_p > (long)limit_t->_hi) return false; // cyclic loop or this loop trips only once } else { long init_p = (long)init_t->_hi + stride_con; if (init_p < (long)min_jint || init_p < (long)limit_t->_lo) return false; // cyclic loop or this loop trips only once } // ================================================= // ---- SUCCESS! Found A Trip-Counted Loop! ----- // assert(x->Opcode() == Op_Loop, "regular loops only"); C->print_method("Before CountedLoop", 3); // If compare points to incr, we are ok. Otherwise the compare // can directly point to the phi; in this case adjust the compare so that // it points to the incr by adjusting the limit. if (cmp->in(1) == phi || cmp->in(2) == phi) limit = gvn->transform(new (C, 3) AddINode(limit,stride)); // trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride. // Final value for iterator should be: trip_count * stride + init_trip. Node *one_p = gvn->intcon( 1); Node *one_m = gvn->intcon(-1); Node *trip_count = NULL; Node *hook = new (C, 6) Node(6); switch( bt ) { case BoolTest::eq: ShouldNotReachHere(); case BoolTest::ne: // Ahh, the case we desire if (stride_con == 1) trip_count = gvn->transform(new (C, 3) SubINode(limit,init_trip)); else if (stride_con == -1) trip_count = gvn->transform(new (C, 3) SubINode(init_trip,limit)); else ShouldNotReachHere(); set_subtree_ctrl(trip_count); //_loop.map(trip_count->_idx,loop(limit)); break; case BoolTest::le: // Maybe convert to '<' case limit = gvn->transform(new (C, 3) AddINode(limit,one_p)); set_subtree_ctrl( limit ); hook->init_req(4, limit); bt = BoolTest::lt; // Make the new limit be in the same loop nest as the old limit //_loop.map(limit->_idx,limit_loop); // Fall into next case case BoolTest::lt: { // Maybe convert to '!=' case if (stride_con < 0) // Count down loop rolls through MAXINT ShouldNotReachHere(); Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip)); set_subtree_ctrl( range ); hook->init_req(0, range); Node *bias = gvn->transform(new (C, 3) AddINode(range,stride)); set_subtree_ctrl( bias ); hook->init_req(1, bias); Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_m)); set_subtree_ctrl( bias1 ); hook->init_req(2, bias1); trip_count = gvn->transform(new (C, 3) DivINode(0,bias1,stride)); set_subtree_ctrl( trip_count ); hook->init_req(3, trip_count); break; } case BoolTest::ge: // Maybe convert to '>' case limit = gvn->transform(new (C, 3) AddINode(limit,one_m)); set_subtree_ctrl( limit ); hook->init_req(4 ,limit); bt = BoolTest::gt; // Make the new limit be in the same loop nest as the old limit //_loop.map(limit->_idx,limit_loop); // Fall into next case case BoolTest::gt: { // Maybe convert to '!=' case if (stride_con > 0) // count up loop rolls through MININT ShouldNotReachHere(); Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip)); set_subtree_ctrl( range ); hook->init_req(0, range); Node *bias = gvn->transform(new (C, 3) AddINode(range,stride)); set_subtree_ctrl( bias ); hook->init_req(1, bias); Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_p)); set_subtree_ctrl( bias1 ); hook->init_req(2, bias1); trip_count = gvn->transform(new (C, 3) DivINode(0,bias1,stride)); set_subtree_ctrl( trip_count ); hook->init_req(3, trip_count); break; } } // switch( bt ) Node *span = gvn->transform(new (C, 3) MulINode(trip_count,stride)); set_subtree_ctrl( span ); hook->init_req(5, span); limit = gvn->transform(new (C, 3) AddINode(span,init_trip)); set_subtree_ctrl( limit ); // Check for SafePoint on backedge and remove Node *sfpt = x->in(LoopNode::LoopBackControl); if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) { lazy_replace( sfpt, iftrue ); loop->_tail = iftrue; } // Build a canonical trip test. // Clone code, as old values may be in use. Node* nphi = PhiNode::make(x, init_trip, TypeInt::INT); nphi = _igvn.register_new_node_with_optimizer(nphi); set_ctrl(nphi, get_ctrl(phi)); incr = incr->clone(); incr->set_req(1,nphi); incr->set_req(2,stride); incr = _igvn.register_new_node_with_optimizer(incr); set_early_ctrl( incr ); nphi->set_req(LoopNode::LoopBackControl, incr); _igvn.replace_node(phi, nphi); phi = nphi->as_Phi(); cmp = cmp->clone(); cmp->set_req(1,incr); cmp->set_req(2,limit); cmp = _igvn.register_new_node_with_optimizer(cmp); set_ctrl(cmp, iff->in(0)); test = test->clone()->as_Bool(); (*(BoolTest*)&test->_test)._test = bt; test->set_req(1,cmp); _igvn.register_new_node_with_optimizer(test); set_ctrl(test, iff->in(0)); // Replace the old IfNode with a new LoopEndNode Node *lex = _igvn.register_new_node_with_optimizer(new (C, 2) CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt )); IfNode *le = lex->as_If(); uint dd = dom_depth(iff); set_idom(le, le->in(0), dd); // Update dominance for loop exit set_loop(le, loop); // Get the loop-exit control Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue)); // Need to swap loop-exit and loop-back control? if (iftrue_op == Op_IfFalse) { Node *ift2=_igvn.register_new_node_with_optimizer(new (C, 1) IfTrueNode (le)); Node *iff2=_igvn.register_new_node_with_optimizer(new (C, 1) IfFalseNode(le)); loop->_tail = back_control = ift2; set_loop(ift2, loop); set_loop(iff2, get_loop(iffalse)); // Lazy update of 'get_ctrl' mechanism. lazy_replace_proj( iffalse, iff2 ); lazy_replace_proj( iftrue, ift2 ); // Swap names iffalse = iff2; iftrue = ift2; } else { _igvn.hash_delete(iffalse); _igvn.hash_delete(iftrue); iffalse->set_req_X( 0, le, &_igvn ); iftrue ->set_req_X( 0, le, &_igvn ); } set_idom(iftrue, le, dd+1); set_idom(iffalse, le, dd+1); assert(iff->outcnt() == 0, "should be dead now"); lazy_replace( iff, le ); // fix 'get_ctrl' // Now setup a new CountedLoopNode to replace the existing LoopNode CountedLoopNode *l = new (C, 3) CountedLoopNode(init_control, back_control); l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve // The following assert is approximately true, and defines the intention // of can_be_counted_loop. It fails, however, because phase->type // is not yet initialized for this loop and its parts. //assert(l->can_be_counted_loop(this), "sanity"); _igvn.register_new_node_with_optimizer(l); set_loop(l, loop); loop->_head = l; // Fix all data nodes placed at the old loop head. // Uses the lazy-update mechanism of 'get_ctrl'. lazy_replace( x, l ); set_idom(l, init_control, dom_depth(x)); // Check for immediately preceding SafePoint and remove Node *sfpt2 = le->in(0); if( sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2)) lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control)); // Free up intermediate goo _igvn.remove_dead_node(hook); #ifdef ASSERT assert(l->is_valid_counted_loop(), "counted loop shape is messed up"); assert(l == loop->_head && l->phi() == phi && l->loopexit() == lex, "" ); #endif C->print_method("After CountedLoop", 3); return true; } //------------------------------Ideal------------------------------------------ // Return a node which is more "ideal" than the current node. // Attempt to convert into a counted-loop. Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) { if (!can_be_counted_loop(phase)) { phase->C->set_major_progress(); } return RegionNode::Ideal(phase, can_reshape); } //============================================================================= //------------------------------Ideal------------------------------------------ // Return a node which is more "ideal" than the current node. // Attempt to convert into a counted-loop. Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) { return RegionNode::Ideal(phase, can_reshape); } //------------------------------dump_spec-------------------------------------- // Dump special per-node info #ifndef PRODUCT void CountedLoopNode::dump_spec(outputStream *st) const { LoopNode::dump_spec(st); if( stride_is_con() ) { st->print("stride: %d ",stride_con()); } else { st->print("stride: not constant "); } if( is_pre_loop () ) st->print("pre of N%d" , _main_idx ); if( is_main_loop() ) st->print("main of N%d", _idx ); if( is_post_loop() ) st->print("post of N%d", _main_idx ); } #endif //============================================================================= int CountedLoopEndNode::stride_con() const { return stride()->bottom_type()->is_int()->get_con(); } //----------------------match_incr_with_optional_truncation-------------------- // Match increment with optional truncation: // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16 // Return NULL for failure. Success returns the increment node. Node* CountedLoopNode::match_incr_with_optional_truncation( Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) { // Quick cutouts: if (expr == NULL || expr->req() != 3) return false; Node *t1 = NULL; Node *t2 = NULL; const TypeInt* trunc_t = TypeInt::INT; Node* n1 = expr; int n1op = n1->Opcode(); // Try to strip (n1 & M) or (n1 << N >> N) from n1. if (n1op == Op_AndI && n1->in(2)->is_Con() && n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) { // %%% This check should match any mask of 2**K-1. t1 = n1; n1 = t1->in(1); n1op = n1->Opcode(); trunc_t = TypeInt::CHAR; } else if (n1op == Op_RShiftI && n1->in(1) != NULL && n1->in(1)->Opcode() == Op_LShiftI && n1->in(2) == n1->in(1)->in(2) && n1->in(2)->is_Con()) { jint shift = n1->in(2)->bottom_type()->is_int()->get_con(); // %%% This check should match any shift in [1..31]. if (shift == 16 || shift == 8) { t1 = n1; t2 = t1->in(1); n1 = t2->in(1); n1op = n1->Opcode(); if (shift == 16) { trunc_t = TypeInt::SHORT; } else if (shift == 8) { trunc_t = TypeInt::BYTE; } } } // If (maybe after stripping) it is an AddI, we won: if (n1op == Op_AddI) { *trunc1 = t1; *trunc2 = t2; *trunc_type = trunc_t; return n1; } // failed return NULL; } //------------------------------filtered_type-------------------------------- // Return a type based on condition control flow // A successful return will be a type that is restricted due // to a series of dominating if-tests, such as: // if (i < 10) { // if (i > 0) { // here: "i" type is [1..10) // } // } // or a control flow merge // if (i < 10) { // do { // phi( , ) -- at top of loop type is [min_int..10) // i = ? // } while ( i < 10) // const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) { assert(n && n->bottom_type()->is_int(), "must be int"); const TypeInt* filtered_t = NULL; if (!n->is_Phi()) { assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control"); filtered_t = filtered_type_from_dominators(n, n_ctrl); } else { Node* phi = n->as_Phi(); Node* region = phi->in(0); assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region"); if (region && region != C->top()) { for (uint i = 1; i < phi->req(); i++) { Node* val = phi->in(i); Node* use_c = region->in(i); const TypeInt* val_t = filtered_type_from_dominators(val, use_c); if (val_t != NULL) { if (filtered_t == NULL) { filtered_t = val_t; } else { filtered_t = filtered_t->meet(val_t)->is_int(); } } } } } const TypeInt* n_t = _igvn.type(n)->is_int(); if (filtered_t != NULL) { n_t = n_t->join(filtered_t)->is_int(); } return n_t; } //------------------------------filtered_type_from_dominators-------------------------------- // Return a possibly more restrictive type for val based on condition control flow of dominators const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) { if (val->is_Con()) { return val->bottom_type()->is_int(); } uint if_limit = 10; // Max number of dominating if's visited const TypeInt* rtn_t = NULL; if (use_ctrl && use_ctrl != C->top()) { Node* val_ctrl = get_ctrl(val); uint val_dom_depth = dom_depth(val_ctrl); Node* pred = use_ctrl; uint if_cnt = 0; while (if_cnt < if_limit) { if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) { if_cnt++; const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred); if (if_t != NULL) { if (rtn_t == NULL) { rtn_t = if_t; } else { rtn_t = rtn_t->join(if_t)->is_int(); } } } pred = idom(pred); if (pred == NULL || pred == C->top()) { break; } // Stop if going beyond definition block of val if (dom_depth(pred) < val_dom_depth) { break; } } } return rtn_t; } //------------------------------dump_spec-------------------------------------- // Dump special per-node info #ifndef PRODUCT void CountedLoopEndNode::dump_spec(outputStream *st) const { if( in(TestValue)->is_Bool() ) { BoolTest bt( test_trip()); // Added this for g++. st->print("["); bt.dump_on(st); st->print("]"); } st->print(" "); IfNode::dump_spec(st); } #endif //============================================================================= //------------------------------is_member-------------------------------------- // Is 'l' a member of 'this'? int IdealLoopTree::is_member( const IdealLoopTree *l ) const { while( l->_nest > _nest ) l = l->_parent; return l == this; } //------------------------------set_nest--------------------------------------- // Set loop tree nesting depth. Accumulate _has_call bits. int IdealLoopTree::set_nest( uint depth ) { _nest = depth; int bits = _has_call; if( _child ) bits |= _child->set_nest(depth+1); if( bits ) _has_call = 1; if( _next ) bits |= _next ->set_nest(depth ); return bits; } //------------------------------split_fall_in---------------------------------- // Split out multiple fall-in edges from the loop header. Move them to a // private RegionNode before the loop. This becomes the loop landing pad. void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) { PhaseIterGVN &igvn = phase->_igvn; uint i; // Make a new RegionNode to be the landing pad. Node *landing_pad = new (phase->C, fall_in_cnt+1) RegionNode( fall_in_cnt+1 ); phase->set_loop(landing_pad,_parent); // Gather all the fall-in control paths into the landing pad uint icnt = fall_in_cnt; uint oreq = _head->req(); for( i = oreq-1; i>0; i-- ) if( !phase->is_member( this, _head->in(i) ) ) landing_pad->set_req(icnt--,_head->in(i)); // Peel off PhiNode edges as well for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { Node *oj = _head->fast_out(j); if( oj->is_Phi() ) { PhiNode* old_phi = oj->as_Phi(); assert( old_phi->region() == _head, "" ); igvn.hash_delete(old_phi); // Yank from hash before hacking edges Node *p = PhiNode::make_blank(landing_pad, old_phi); uint icnt = fall_in_cnt; for( i = oreq-1; i>0; i-- ) { if( !phase->is_member( this, _head->in(i) ) ) { p->init_req(icnt--, old_phi->in(i)); // Go ahead and clean out old edges from old phi old_phi->del_req(i); } } // Search for CSE's here, because ZKM.jar does a lot of // loop hackery and we need to be a little incremental // with the CSE to avoid O(N^2) node blow-up. Node *p2 = igvn.hash_find_insert(p); // Look for a CSE if( p2 ) { // Found CSE p->destruct(); // Recover useless new node p = p2; // Use old node } else { igvn.register_new_node_with_optimizer(p, old_phi); } // Make old Phi refer to new Phi. old_phi->add_req(p); // Check for the special case of making the old phi useless and // disappear it. In JavaGrande I have a case where this useless // Phi is the loop limit and prevents recognizing a CountedLoop // which in turn prevents removing an empty loop. Node *id_old_phi = old_phi->Identity( &igvn ); if( id_old_phi != old_phi ) { // Found a simple identity? // Note that I cannot call 'replace_node' here, because // that will yank the edge from old_phi to the Region and // I'm mid-iteration over the Region's uses. for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) { Node* use = old_phi->last_out(i); igvn.hash_delete(use); igvn._worklist.push(use); uint uses_found = 0; for (uint j = 0; j < use->len(); j++) { if (use->in(j) == old_phi) { if (j < use->req()) use->set_req (j, id_old_phi); else use->set_prec(j, id_old_phi); uses_found++; } } i -= uses_found; // we deleted 1 or more copies of this edge } } igvn._worklist.push(old_phi); } } // Finally clean out the fall-in edges from the RegionNode for( i = oreq-1; i>0; i-- ) { if( !phase->is_member( this, _head->in(i) ) ) { _head->del_req(i); } } // Transform landing pad igvn.register_new_node_with_optimizer(landing_pad, _head); // Insert landing pad into the header _head->add_req(landing_pad); } //------------------------------split_outer_loop------------------------------- // Split out the outermost loop from this shared header. void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) { PhaseIterGVN &igvn = phase->_igvn; // Find index of outermost loop; it should also be my tail. uint outer_idx = 1; while( _head->in(outer_idx) != _tail ) outer_idx++; // Make a LoopNode for the outermost loop. Node *ctl = _head->in(LoopNode::EntryControl); Node *outer = new (phase->C, 3) LoopNode( ctl, _head->in(outer_idx) ); outer = igvn.register_new_node_with_optimizer(outer, _head); phase->set_created_loop_node(); // Outermost loop falls into '_head' loop _head->set_req(LoopNode::EntryControl, outer); _head->del_req(outer_idx); // Split all the Phis up between '_head' loop and 'outer' loop. for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { Node *out = _head->fast_out(j); if( out->is_Phi() ) { PhiNode *old_phi = out->as_Phi(); assert( old_phi->region() == _head, "" ); Node *phi = PhiNode::make_blank(outer, old_phi); phi->init_req(LoopNode::EntryControl, old_phi->in(LoopNode::EntryControl)); phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx)); phi = igvn.register_new_node_with_optimizer(phi, old_phi); // Make old Phi point to new Phi on the fall-in path igvn.hash_delete(old_phi); old_phi->set_req(LoopNode::EntryControl, phi); old_phi->del_req(outer_idx); igvn._worklist.push(old_phi); } } // Use the new loop head instead of the old shared one _head = outer; phase->set_loop(_head, this); } //------------------------------fix_parent------------------------------------- static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) { loop->_parent = parent; if( loop->_child ) fix_parent( loop->_child, loop ); if( loop->_next ) fix_parent( loop->_next , parent ); } //------------------------------estimate_path_freq----------------------------- static float estimate_path_freq( Node *n ) { // Try to extract some path frequency info IfNode *iff; for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests uint nop = n->Opcode(); if( nop == Op_SafePoint ) { // Skip any safepoint n = n->in(0); continue; } if( nop == Op_CatchProj ) { // Get count from a prior call // Assume call does not always throw exceptions: means the call-site // count is also the frequency of the fall-through path. assert( n->is_CatchProj(), "" ); if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index ) return 0.0f; // Assume call exception path is rare Node *call = n->in(0)->in(0)->in(0); assert( call->is_Call(), "expect a call here" ); const JVMState *jvms = ((CallNode*)call)->jvms(); ciMethodData* methodData = jvms->method()->method_data(); if (!methodData->is_mature()) return 0.0f; // No call-site data ciProfileData* data = methodData->bci_to_data(jvms->bci()); if ((data == NULL) || !data->is_CounterData()) { // no call profile available, try call's control input n = n->in(0); continue; } return data->as_CounterData()->count()/FreqCountInvocations; } // See if there's a gating IF test Node *n_c = n->in(0); if( !n_c->is_If() ) break; // No estimate available iff = n_c->as_If(); if( iff->_fcnt != COUNT_UNKNOWN ) // Have a valid count? // Compute how much count comes on this path return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt; // Have no count info. Skip dull uncommon-trap like branches. if( (nop == Op_IfTrue && iff->_prob < PROB_LIKELY_MAG(5)) || (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) ) break; // Skip through never-taken branch; look for a real loop exit. n = iff->in(0); } return 0.0f; // No estimate available } //------------------------------merge_many_backedges--------------------------- // Merge all the backedges from the shared header into a private Region. // Feed that region as the one backedge to this loop. void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) { uint i; // Scan for the top 2 hottest backedges float hotcnt = 0.0f; float warmcnt = 0.0f; uint hot_idx = 0; // Loop starts at 2 because slot 1 is the fall-in path for( i = 2; i < _head->req(); i++ ) { float cnt = estimate_path_freq(_head->in(i)); if( cnt > hotcnt ) { // Grab hottest path warmcnt = hotcnt; hotcnt = cnt; hot_idx = i; } else if( cnt > warmcnt ) { // And 2nd hottest path warmcnt = cnt; } } // See if the hottest backedge is worthy of being an inner loop // by being much hotter than the next hottest backedge. if( hotcnt <= 0.0001 || hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge // Peel out the backedges into a private merge point; peel // them all except optionally hot_idx. PhaseIterGVN &igvn = phase->_igvn; Node *hot_tail = NULL; // Make a Region for the merge point Node *r = new (phase->C, 1) RegionNode(1); for( i = 2; i < _head->req(); i++ ) { if( i != hot_idx ) r->add_req( _head->in(i) ); else hot_tail = _head->in(i); } igvn.register_new_node_with_optimizer(r, _head); // Plug region into end of loop _head, followed by hot_tail while( _head->req() > 3 ) _head->del_req( _head->req()-1 ); _head->set_req(2, r); if( hot_idx ) _head->add_req(hot_tail); // Split all the Phis up between '_head' loop and the Region 'r' for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) { Node *out = _head->fast_out(j); if( out->is_Phi() ) { PhiNode* n = out->as_Phi(); igvn.hash_delete(n); // Delete from hash before hacking edges Node *hot_phi = NULL; Node *phi = new (phase->C, r->req()) PhiNode(r, n->type(), n->adr_type()); // Check all inputs for the ones to peel out uint j = 1; for( uint i = 2; i < n->req(); i++ ) { if( i != hot_idx ) phi->set_req( j++, n->in(i) ); else hot_phi = n->in(i); } // Register the phi but do not transform until whole place transforms igvn.register_new_node_with_optimizer(phi, n); // Add the merge phi to the old Phi while( n->req() > 3 ) n->del_req( n->req()-1 ); n->set_req(2, phi); if( hot_idx ) n->add_req(hot_phi); } } // Insert a new IdealLoopTree inserted below me. Turn it into a clone // of self loop tree. Turn self into a loop headed by _head and with // tail being the new merge point. IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail ); phase->set_loop(_tail,ilt); // Adjust tail _tail = r; // Self's tail is new merge point phase->set_loop(r,this); ilt->_child = _child; // New guy has my children _child = ilt; // Self has new guy as only child ilt->_parent = this; // new guy has self for parent ilt->_nest = _nest; // Same nesting depth (for now) // Starting with 'ilt', look for child loop trees using the same shared // header. Flatten these out; they will no longer be loops in the end. IdealLoopTree **pilt = &_child; while( ilt ) { if( ilt->_head == _head ) { uint i; for( i = 2; i < _head->req(); i++ ) if( _head->in(i) == ilt->_tail ) break; // Still a loop if( i == _head->req() ) { // No longer a loop // Flatten ilt. Hang ilt's "_next" list from the end of // ilt's '_child' list. Move the ilt's _child up to replace ilt. IdealLoopTree **cp = &ilt->_child; while( *cp ) cp = &(*cp)->_next; // Find end of child list *cp = ilt->_next; // Hang next list at end of child list *pilt = ilt->_child; // Move child up to replace ilt ilt->_head = NULL; // Flag as a loop UNIONED into parent ilt = ilt->_child; // Repeat using new ilt continue; // do not advance over ilt->_child } assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" ); phase->set_loop(_head,ilt); } pilt = &ilt->_child; // Advance to next ilt = *pilt; } if( _child ) fix_parent( _child, this ); } //------------------------------beautify_loops--------------------------------- // Split shared headers and insert loop landing pads. // Insert a LoopNode to replace the RegionNode. // Return TRUE if loop tree is structurally changed. bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) { bool result = false; // Cache parts in locals for easy PhaseIterGVN &igvn = phase->_igvn; phase->C->print_method("Before beautify loops", 3); igvn.hash_delete(_head); // Yank from hash before hacking edges // Check for multiple fall-in paths. Peel off a landing pad if need be. int fall_in_cnt = 0; for( uint i = 1; i < _head->req(); i++ ) if( !phase->is_member( this, _head->in(i) ) ) fall_in_cnt++; assert( fall_in_cnt, "at least 1 fall-in path" ); if( fall_in_cnt > 1 ) // Need a loop landing pad to merge fall-ins split_fall_in( phase, fall_in_cnt ); // Swap inputs to the _head and all Phis to move the fall-in edge to // the left. fall_in_cnt = 1; while( phase->is_member( this, _head->in(fall_in_cnt) ) ) fall_in_cnt++; if( fall_in_cnt > 1 ) { // Since I am just swapping inputs I do not need to update def-use info Node *tmp = _head->in(1); _head->set_req( 1, _head->in(fall_in_cnt) ); _head->set_req( fall_in_cnt, tmp ); // Swap also all Phis for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) { Node* phi = _head->fast_out(i); if( phi->is_Phi() ) { igvn.hash_delete(phi); // Yank from hash before hacking edges tmp = phi->in(1); phi->set_req( 1, phi->in(fall_in_cnt) ); phi->set_req( fall_in_cnt, tmp ); } } } assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" ); assert( phase->is_member( this, _head->in(2) ), "right edge is loop" ); // If I am a shared header (multiple backedges), peel off the many // backedges into a private merge point and use the merge point as // the one true backedge. if( _head->req() > 3 ) { // Merge the many backedges into a single backedge. merge_many_backedges( phase ); result = true; } // If I am a shared header (multiple backedges), peel off myself loop. // I better be the outermost loop. if( _head->req() > 3 ) { split_outer_loop( phase ); result = true; } else if( !_head->is_Loop() && !_irreducible ) { // Make a new LoopNode to replace the old loop head Node *l = new (phase->C, 3) LoopNode( _head->in(1), _head->in(2) ); l = igvn.register_new_node_with_optimizer(l, _head); phase->set_created_loop_node(); // Go ahead and replace _head phase->_igvn.replace_node( _head, l ); _head = l; phase->set_loop(_head, this); } // Now recursively beautify nested loops if( _child ) result |= _child->beautify_loops( phase ); if( _next ) result |= _next ->beautify_loops( phase ); return result; } //------------------------------allpaths_check_safepts---------------------------- // Allpaths backwards scan from loop tail, terminating each path at first safepoint // encountered. Helper for check_safepts. void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) { assert(stack.size() == 0, "empty stack"); stack.push(_tail); visited.Clear(); visited.set(_tail->_idx); while (stack.size() > 0) { Node* n = stack.pop(); if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) { // Terminate this path } else if (n->Opcode() == Op_SafePoint) { if (_phase->get_loop(n) != this) { if (_required_safept == NULL) _required_safept = new Node_List(); _required_safept->push(n); // save the one closest to the tail } // Terminate this path } else { uint start = n->is_Region() ? 1 : 0; uint end = n->is_Region() && !n->is_Loop() ? n->req() : start + 1; for (uint i = start; i < end; i++) { Node* in = n->in(i); assert(in->is_CFG(), "must be"); if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) { stack.push(in); } } } } } //------------------------------check_safepts---------------------------- // Given dominators, try to find loops with calls that must always be // executed (call dominates loop tail). These loops do not need non-call // safepoints (ncsfpt). // // A complication is that a safepoint in a inner loop may be needed // by an outer loop. In the following, the inner loop sees it has a // call (block 3) on every path from the head (block 2) to the // backedge (arc 3->2). So it deletes the ncsfpt (non-call safepoint) // in block 2, _but_ this leaves the outer loop without a safepoint. // // entry 0 // | // v // outer 1,2 +->1 // | | // | v // | 2<---+ ncsfpt in 2 // |_/|\ | // | v | // inner 2,3 / 3 | call in 3 // / | | // v +--+ // exit 4 // // // This method creates a list (_required_safept) of ncsfpt nodes that must // be protected is created for each loop. When a ncsfpt maybe deleted, it // is first looked for in the lists for the outer loops of the current loop. // // The insights into the problem: // A) counted loops are okay // B) innermost loops are okay (only an inner loop can delete // a ncsfpt needed by an outer loop) // C) a loop is immune from an inner loop deleting a safepoint // if the loop has a call on the idom-path // D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the // idom-path that is not in a nested loop // E) otherwise, an ncsfpt on the idom-path that is nested in an inner // loop needs to be prevented from deletion by an inner loop // // There are two analyses: // 1) The first, and cheaper one, scans the loop body from // tail to head following the idom (immediate dominator) // chain, looking for the cases (C,D,E) above. // Since inner loops are scanned before outer loops, there is summary // information about inner loops. Inner loops can be skipped over // when the tail of an inner loop is encountered. // // 2) The second, invoked if the first fails to find a call or ncsfpt on // the idom path (which is rare), scans all predecessor control paths // from the tail to the head, terminating a path when a call or sfpt // is encountered, to find the ncsfpt's that are closest to the tail. // void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) { // Bottom up traversal IdealLoopTree* ch = _child; while (ch != NULL) { ch->check_safepts(visited, stack); ch = ch->_next; } if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) { bool has_call = false; // call on dom-path bool has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth Node* nonlocal_ncsfpt = NULL; // ncsfpt on dom-path at a deeper depth // Scan the dom-path nodes from tail to head for (Node* n = tail(); n != _head; n = _phase->idom(n)) { if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) { has_call = true; _has_sfpt = 1; // Then no need for a safept! break; } else if (n->Opcode() == Op_SafePoint) { if (_phase->get_loop(n) == this) { has_local_ncsfpt = true; break; } if (nonlocal_ncsfpt == NULL) { nonlocal_ncsfpt = n; // save the one closest to the tail } } else { IdealLoopTree* nlpt = _phase->get_loop(n); if (this != nlpt) { // If at an inner loop tail, see if the inner loop has already // recorded seeing a call on the dom-path (and stop.) If not, // jump to the head of the inner loop. assert(is_member(nlpt), "nested loop"); Node* tail = nlpt->_tail; if (tail->in(0)->is_If()) tail = tail->in(0); if (n == tail) { // If inner loop has call on dom-path, so does outer loop if (nlpt->_has_sfpt) { has_call = true; _has_sfpt = 1; break; } // Skip to head of inner loop assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head"); n = nlpt->_head; } } } } // Record safept's that this loop needs preserved when an // inner loop attempts to delete it's safepoints. if (_child != NULL && !has_call && !has_local_ncsfpt) { if (nonlocal_ncsfpt != NULL) { if (_required_safept == NULL) _required_safept = new Node_List(); _required_safept->push(nonlocal_ncsfpt); } else { // Failed to find a suitable safept on the dom-path. Now use // an all paths walk from tail to head, looking for safepoints to preserve. allpaths_check_safepts(visited, stack); } } } } //---------------------------is_deleteable_safept---------------------------- // Is safept not required by an outer loop? bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) { assert(sfpt->Opcode() == Op_SafePoint, ""); IdealLoopTree* lp = get_loop(sfpt)->_parent; while (lp != NULL) { Node_List* sfpts = lp->_required_safept; if (sfpts != NULL) { for (uint i = 0; i < sfpts->size(); i++) { if (sfpt == sfpts->at(i)) return false; } } lp = lp->_parent; } return true; } //---------------------------replace_parallel_iv------------------------------- // Replace parallel induction variable (parallel to trip counter) void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) { assert(loop->_head->is_CountedLoop(), ""); CountedLoopNode *cl = loop->_head->as_CountedLoop(); Node *incr = cl->incr(); if (incr == NULL) return; // Dead loop? Node *init = cl->init_trip(); Node *phi = cl->phi(); // protect against stride not being a constant if (!cl->stride_is_con()) return; int stride_con = cl->stride_con(); PhaseGVN *gvn = &_igvn; // Visit all children, looking for Phis for (DUIterator i = cl->outs(); cl->has_out(i); i++) { Node *out = cl->out(i); // Look for other phis (secondary IVs). Skip dead ones if (!out->is_Phi() || out == phi || !has_node(out)) continue; PhiNode* phi2 = out->as_Phi(); Node *incr2 = phi2->in( LoopNode::LoopBackControl ); // Look for induction variables of the form: X += constant if (phi2->region() != loop->_head || incr2->req() != 3 || incr2->in(1) != phi2 || incr2 == incr || incr2->Opcode() != Op_AddI || !incr2->in(2)->is_Con()) continue; // Check for parallel induction variable (parallel to trip counter) // via an affine function. In particular, count-down loops with // count-up array indices are common. We only RCE references off // the trip-counter, so we need to convert all these to trip-counter // expressions. Node *init2 = phi2->in( LoopNode::EntryControl ); int stride_con2 = incr2->in(2)->get_int(); // The general case here gets a little tricky. We want to find the // GCD of all possible parallel IV's and make a new IV using this // GCD for the loop. Then all possible IVs are simple multiples of // the GCD. In practice, this will cover very few extra loops. // Instead we require 'stride_con2' to be a multiple of 'stride_con', // where +/-1 is the common case, but other integer multiples are // also easy to handle. int ratio_con = stride_con2/stride_con; if ((ratio_con * stride_con) == stride_con2) { // Check for exact // Convert to using the trip counter. The parallel induction // variable differs from the trip counter by a loop-invariant // amount, the difference between their respective initial values. // It is scaled by the 'ratio_con'. // Perform local Ideal transformation since in most cases ratio == 1. Node* ratio = _igvn.intcon(ratio_con); set_ctrl(ratio, C->root()); Node* hook = new (C, 3) Node(3); Node* ratio_init = gvn->transform(new (C, 3) MulINode(init, ratio)); hook->init_req(0, ratio_init); Node* diff = gvn->transform(new (C, 3) SubINode(init2, ratio_init)); hook->init_req(1, diff); Node* ratio_idx = gvn->transform(new (C, 3) MulINode(phi, ratio)); hook->init_req(2, ratio_idx); Node* add = gvn->transform(new (C, 3) AddINode(ratio_idx, diff)); set_subtree_ctrl(add); _igvn.replace_node( phi2, add ); // Free up intermediate goo _igvn.remove_dead_node(hook); // Sometimes an induction variable is unused if (add->outcnt() == 0) { _igvn.remove_dead_node(add); } --i; // deleted this phi; rescan starting with next position continue; } } } //------------------------------counted_loop----------------------------------- // Convert to counted loops where possible void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) { // For grins, set the inner-loop flag here if (!_child) { if (_head->is_Loop()) _head->as_Loop()->set_inner_loop(); } if (_head->is_CountedLoop() || phase->is_counted_loop(_head, this)) { _has_sfpt = 1; // Indicate we do not need a safepoint here // Look for a safepoint to remove for (Node* n = tail(); n != _head; n = phase->idom(n)) if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this && phase->is_deleteable_safept(n)) phase->lazy_replace(n,n->in(TypeFunc::Control)); // Look for induction variables phase->replace_parallel_iv(this); } else if (_parent != NULL && !_irreducible) { // Not a counted loop. // Look for a safepoint on the idom-path to remove, preserving the first one bool found = false; Node* n = tail(); for (; n != _head && !found; n = phase->idom(n)) { if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this) found = true; // Found one } // Skip past it and delete the others for (; n != _head; n = phase->idom(n)) { if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this && phase->is_deleteable_safept(n)) phase->lazy_replace(n,n->in(TypeFunc::Control)); } } // Recursively if (_child) _child->counted_loop( phase ); if (_next) _next ->counted_loop( phase ); } #ifndef PRODUCT //------------------------------dump_head-------------------------------------- // Dump 1 liner for loop header info void IdealLoopTree::dump_head( ) const { for (uint i=0; i<_nest; i++) tty->print(" "); tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx); if (_irreducible) tty->print(" IRREDUCIBLE"); if (UseLoopPredicate) { Node* entry = _head->in(LoopNode::EntryControl); if (entry != NULL && entry->is_Proj() && PhaseIdealLoop::is_uncommon_trap_if_pattern(entry->as_Proj(), Deoptimization::Reason_predicate)) { tty->print(" predicated"); } } if (_head->is_CountedLoop()) { CountedLoopNode *cl = _head->as_CountedLoop(); tty->print(" counted"); if (cl->is_pre_loop ()) tty->print(" pre" ); if (cl->is_main_loop()) tty->print(" main"); if (cl->is_post_loop()) tty->print(" post"); } tty->cr(); } //------------------------------dump------------------------------------------- // Dump loops by loop tree void IdealLoopTree::dump( ) const { dump_head(); if (_child) _child->dump(); if (_next) _next ->dump(); } #endif static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) { if (loop == root) { if (loop->_child != NULL) { log->begin_head("loop_tree"); log->end_head(); if( loop->_child ) log_loop_tree(root, loop->_child, log); log->tail("loop_tree"); assert(loop->_next == NULL, "what?"); } } else { Node* head = loop->_head; log->begin_head("loop"); log->print(" idx='%d' ", head->_idx); if (loop->_irreducible) log->print("irreducible='1' "); if (head->is_Loop()) { if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' "); if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' "); } if (head->is_CountedLoop()) { CountedLoopNode* cl = head->as_CountedLoop(); if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx()); if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx); if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx()); } log->end_head(); if( loop->_child ) log_loop_tree(root, loop->_child, log); log->tail("loop"); if( loop->_next ) log_loop_tree(root, loop->_next, log); } } //---------------------collect_potentially_useful_predicates----------------------- // Helper function to collect potentially useful predicates to prevent them from // being eliminated by PhaseIdealLoop::eliminate_useless_predicates void PhaseIdealLoop::collect_potentially_useful_predicates( IdealLoopTree * loop, Unique_Node_List &useful_predicates) { if (loop->_child) { // child collect_potentially_useful_predicates(loop->_child, useful_predicates); } // self (only loops that we can apply loop predication may use their predicates) if (loop->_head->is_Loop() && !loop->_irreducible && !loop->tail()->is_top()) { LoopNode* lpn = loop->_head->as_Loop(); Node* entry = lpn->in(LoopNode::EntryControl); Node* predicate_proj = find_predicate(entry); if (predicate_proj != NULL ) { // right pattern that can be used by loop predication assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be"); useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one } } if (loop->_next) { // sibling collect_potentially_useful_predicates(loop->_next, useful_predicates); } } //------------------------eliminate_useless_predicates----------------------------- // Eliminate all inserted predicates if they could not be used by loop predication. void PhaseIdealLoop::eliminate_useless_predicates() { if (C->predicate_count() == 0) return; // no predicate left Unique_Node_List useful_predicates; // to store useful predicates if (C->has_loops()) { collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates); } for (int i = C->predicate_count(); i > 0; i--) { Node * n = C->predicate_opaque1_node(i-1); assert(n->Opcode() == Op_Opaque1, "must be"); if (!useful_predicates.member(n)) { // not in the useful list _igvn.replace_node(n, n->in(1)); } } } //============================================================================= //----------------------------build_and_optimize------------------------------- // Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to // its corresponding LoopNode. If 'optimize' is true, do some loop cleanups. void PhaseIdealLoop::build_and_optimize(bool do_split_ifs, bool do_loop_pred) { ResourceMark rm; int old_progress = C->major_progress(); // Reset major-progress flag for the driver's heuristics C->clear_major_progress(); #ifndef PRODUCT // Capture for later assert uint unique = C->unique(); _loop_invokes++; _loop_work += unique; #endif // True if the method has at least 1 irreducible loop _has_irreducible_loops = false; _created_loop_node = false; Arena *a = Thread::current()->resource_area(); VectorSet visited(a); // Pre-grow the mapping from Nodes to IdealLoopTrees. _nodes.map(C->unique(), NULL); memset(_nodes.adr(), 0, wordSize * C->unique()); // Pre-build the top-level outermost loop tree entry _ltree_root = new IdealLoopTree( this, C->root(), C->root() ); // Do not need a safepoint at the top level _ltree_root->_has_sfpt = 1; // Empty pre-order array allocate_preorders(); // Build a loop tree on the fly. Build a mapping from CFG nodes to // IdealLoopTree entries. Data nodes are NOT walked. build_loop_tree(); // Check for bailout, and return if (C->failing()) { return; } // No loops after all if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false); // There should always be an outer loop containing the Root and Return nodes. // If not, we have a degenerate empty program. Bail out in this case. if (!has_node(C->root())) { if (!_verify_only) { C->clear_major_progress(); C->record_method_not_compilable("empty program detected during loop optimization"); } return; } // Nothing to do, so get out if( !C->has_loops() && !do_split_ifs && !_verify_me && !_verify_only ) { _igvn.optimize(); // Cleanup NeverBranches return; } // Set loop nesting depth _ltree_root->set_nest( 0 ); // Split shared headers and insert loop landing pads. // Do not bother doing this on the Root loop of course. if( !_verify_me && !_verify_only && _ltree_root->_child ) { if( _ltree_root->_child->beautify_loops( this ) ) { // Re-build loop tree! _ltree_root->_child = NULL; _nodes.clear(); reallocate_preorders(); build_loop_tree(); // Check for bailout, and return if (C->failing()) { return; } // Reset loop nesting depth _ltree_root->set_nest( 0 ); C->print_method("After beautify loops", 3); } } // Build Dominators for elision of NULL checks & loop finding. // Since nodes do not have a slot for immediate dominator, make // a persistent side array for that info indexed on node->_idx. _idom_size = C->unique(); _idom = NEW_RESOURCE_ARRAY( Node*, _idom_size ); _dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size ); _dom_stk = NULL; // Allocated on demand in recompute_dom_depth memset( _dom_depth, 0, _idom_size * sizeof(uint) ); Dominators(); if (!_verify_only) { // As a side effect, Dominators removed any unreachable CFG paths // into RegionNodes. It doesn't do this test against Root, so // we do it here. for( uint i = 1; i < C->root()->req(); i++ ) { if( !_nodes[C->root()->in(i)->_idx] ) { // Dead path into Root? _igvn.hash_delete(C->root()); C->root()->del_req(i); _igvn._worklist.push(C->root()); i--; // Rerun same iteration on compressed edges } } // Given dominators, try to find inner loops with calls that must // always be executed (call dominates loop tail). These loops do // not need a separate safepoint. Node_List cisstack(a); _ltree_root->check_safepts(visited, cisstack); } // Walk the DATA nodes and place into loops. Find earliest control // node. For CFG nodes, the _nodes array starts out and remains // holding the associated IdealLoopTree pointer. For DATA nodes, the // _nodes array holds the earliest legal controlling CFG node. // Allocate stack with enough space to avoid frequent realloc int stack_size = (C->unique() >> 1) + 16; // (unique>>1)+16 from Java2D stats Node_Stack nstack( a, stack_size ); visited.Clear(); Node_List worklist(a); // Don't need C->root() on worklist since // it will be processed among C->top() inputs worklist.push( C->top() ); visited.set( C->top()->_idx ); // Set C->top() as visited now build_loop_early( visited, worklist, nstack ); // Given early legal placement, try finding counted loops. This placement // is good enough to discover most loop invariants. if( !_verify_me && !_verify_only ) _ltree_root->counted_loop( this ); // Find latest loop placement. Find ideal loop placement. visited.Clear(); init_dom_lca_tags(); // Need C->root() on worklist when processing outs worklist.push( C->root() ); NOT_PRODUCT( C->verify_graph_edges(); ) worklist.push( C->top() ); build_loop_late( visited, worklist, nstack ); if (_verify_only) { // restore major progress flag for (int i = 0; i < old_progress; i++) C->set_major_progress(); assert(C->unique() == unique, "verification mode made Nodes? ? ?"); assert(_igvn._worklist.size() == 0, "shouldn't push anything"); return; } // some parser-inserted loop predicates could never be used by loop // predication. Eliminate them before loop optimization if (UseLoopPredicate) { eliminate_useless_predicates(); } // clear out the dead code while(_deadlist.size()) { _igvn.remove_globally_dead_node(_deadlist.pop()); } #ifndef PRODUCT C->verify_graph_edges(); if (_verify_me) { // Nested verify pass? // Check to see if the verify mode is broken assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?"); return; } if(VerifyLoopOptimizations) verify(); if(TraceLoopOpts && C->has_loops()) { _ltree_root->dump(); } #endif if (ReassociateInvariants) { // Reassociate invariants and prep for split_thru_phi for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { IdealLoopTree* lpt = iter.current(); if (!lpt->is_counted() || !lpt->is_inner()) continue; lpt->reassociate_invariants(this); // Because RCE opportunities can be masked by split_thru_phi, // look for RCE candidates and inhibit split_thru_phi // on just their loop-phi's for this pass of loop opts if (SplitIfBlocks && do_split_ifs) { if (lpt->policy_range_check(this)) { lpt->_rce_candidate = 1; // = true } } } } // Check for aggressive application of split-if and other transforms // that require basic-block info (like cloning through Phi's) if( SplitIfBlocks && do_split_ifs ) { visited.Clear(); split_if_with_blocks( visited, nstack ); NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); ); } // Perform loop predication before iteration splitting if (do_loop_pred && C->has_loops() && !C->major_progress()) { _ltree_root->_child->loop_predication(this); } if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) { if (do_intrinsify_fill()) { C->set_major_progress(); } } // Perform iteration-splitting on inner loops. Split iterations to avoid // range checks or one-shot null checks. // If split-if's didn't hack the graph too bad (no CFG changes) // then do loop opts. if (C->has_loops() && !C->major_progress()) { memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) ); _ltree_root->_child->iteration_split( this, worklist ); // No verify after peeling! GCM has hoisted code out of the loop. // After peeling, the hoisted code could sink inside the peeled area. // The peeling code does not try to recompute the best location for // all the code before the peeled area, so the verify pass will always // complain about it. } // Do verify graph edges in any case NOT_PRODUCT( C->verify_graph_edges(); ); if (!do_split_ifs) { // We saw major progress in Split-If to get here. We forced a // pass with unrolling and not split-if, however more split-if's // might make progress. If the unrolling didn't make progress // then the major-progress flag got cleared and we won't try // another round of Split-If. In particular the ever-common // instance-of/check-cast pattern requires at least 2 rounds of // Split-If to clear out. C->set_major_progress(); } // Repeat loop optimizations if new loops were seen if (created_loop_node()) { C->set_major_progress(); } // Convert scalar to superword operations if (UseSuperWord && C->has_loops() && !C->major_progress()) { // SuperWord transform SuperWord sw(this); for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { IdealLoopTree* lpt = iter.current(); if (lpt->is_counted()) { sw.transform_loop(lpt); } } } // Cleanup any modified bits _igvn.optimize(); // disable assert until issue with split_flow_path is resolved (6742111) // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(), // "shouldn't introduce irreducible loops"); if (C->log() != NULL) { log_loop_tree(_ltree_root, _ltree_root, C->log()); } } #ifndef PRODUCT //------------------------------print_statistics------------------------------- int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique void PhaseIdealLoop::print_statistics() { tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work); } //------------------------------verify----------------------------------------- // Build a verify-only PhaseIdealLoop, and see that it agrees with me. static int fail; // debug only, so its multi-thread dont care void PhaseIdealLoop::verify() const { int old_progress = C->major_progress(); ResourceMark rm; PhaseIdealLoop loop_verify( _igvn, this ); VectorSet visited(Thread::current()->resource_area()); fail = 0; verify_compare( C->root(), &loop_verify, visited ); assert( fail == 0, "verify loops failed" ); // Verify loop structure is the same _ltree_root->verify_tree(loop_verify._ltree_root, NULL); // Reset major-progress. It was cleared by creating a verify version of // PhaseIdealLoop. for( int i=0; iset_major_progress(); } //------------------------------verify_compare--------------------------------- // Make sure me and the given PhaseIdealLoop agree on key data structures void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const { if( !n ) return; if( visited.test_set( n->_idx ) ) return; if( !_nodes[n->_idx] ) { // Unreachable assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" ); return; } uint i; for( i = 0; i < n->req(); i++ ) verify_compare( n->in(i), loop_verify, visited ); // Check the '_nodes' block/loop structure i = n->_idx; if( has_ctrl(n) ) { // We have control; verify has loop or ctrl if( _nodes[i] != loop_verify->_nodes[i] && get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) { tty->print("Mismatched control setting for: "); n->dump(); if( fail++ > 10 ) return; Node *c = get_ctrl_no_update(n); tty->print("We have it as: "); if( c->in(0) ) c->dump(); else tty->print_cr("N%d",c->_idx); tty->print("Verify thinks: "); if( loop_verify->has_ctrl(n) ) loop_verify->get_ctrl_no_update(n)->dump(); else loop_verify->get_loop_idx(n)->dump(); tty->cr(); } } else { // We have a loop IdealLoopTree *us = get_loop_idx(n); if( loop_verify->has_ctrl(n) ) { tty->print("Mismatched loop setting for: "); n->dump(); if( fail++ > 10 ) return; tty->print("We have it as: "); us->dump(); tty->print("Verify thinks: "); loop_verify->get_ctrl_no_update(n)->dump(); tty->cr(); } else if (!C->major_progress()) { // Loop selection can be messed up if we did a major progress // operation, like split-if. Do not verify in that case. IdealLoopTree *them = loop_verify->get_loop_idx(n); if( us->_head != them->_head || us->_tail != them->_tail ) { tty->print("Unequals loops for: "); n->dump(); if( fail++ > 10 ) return; tty->print("We have it as: "); us->dump(); tty->print("Verify thinks: "); them->dump(); tty->cr(); } } } // Check for immediate dominators being equal if( i >= _idom_size ) { if( !n->is_CFG() ) return; tty->print("CFG Node with no idom: "); n->dump(); return; } if( !n->is_CFG() ) return; if( n == C->root() ) return; // No IDOM here assert(n->_idx == i, "sanity"); Node *id = idom_no_update(n); if( id != loop_verify->idom_no_update(n) ) { tty->print("Unequals idoms for: "); n->dump(); if( fail++ > 10 ) return; tty->print("We have it as: "); id->dump(); tty->print("Verify thinks: "); loop_verify->idom_no_update(n)->dump(); tty->cr(); } } //------------------------------verify_tree------------------------------------ // Verify that tree structures match. Because the CFG can change, siblings // within the loop tree can be reordered. We attempt to deal with that by // reordering the verify's loop tree if possible. void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const { assert( _parent == parent, "Badly formed loop tree" ); // Siblings not in same order? Attempt to re-order. if( _head != loop->_head ) { // Find _next pointer to update IdealLoopTree **pp = &loop->_parent->_child; while( *pp != loop ) pp = &((*pp)->_next); // Find proper sibling to be next IdealLoopTree **nn = &loop->_next; while( (*nn) && (*nn)->_head != _head ) nn = &((*nn)->_next); // Check for no match. if( !(*nn) ) { // Annoyingly, irreducible loops can pick different headers // after a major_progress operation, so the rest of the loop // tree cannot be matched. if (_irreducible && Compile::current()->major_progress()) return; assert( 0, "failed to match loop tree" ); } // Move (*nn) to (*pp) IdealLoopTree *hit = *nn; *nn = hit->_next; hit->_next = loop; *pp = loop; loop = hit; // Now try again to verify } assert( _head == loop->_head , "mismatched loop head" ); Node *tail = _tail; // Inline a non-updating version of while( !tail->in(0) ) // the 'tail()' call. tail = tail->in(1); assert( tail == loop->_tail, "mismatched loop tail" ); // Counted loops that are guarded should be able to find their guards if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) { CountedLoopNode *cl = _head->as_CountedLoop(); Node *init = cl->init_trip(); Node *ctrl = cl->in(LoopNode::EntryControl); assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); Node *iff = ctrl->in(0); assert( iff->Opcode() == Op_If, "" ); Node *bol = iff->in(1); assert( bol->Opcode() == Op_Bool, "" ); Node *cmp = bol->in(1); assert( cmp->Opcode() == Op_CmpI, "" ); Node *add = cmp->in(1); Node *opaq; if( add->Opcode() == Op_Opaque1 ) { opaq = add; } else { assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" ); assert( add == init, "" ); opaq = cmp->in(2); } assert( opaq->Opcode() == Op_Opaque1, "" ); } if (_child != NULL) _child->verify_tree(loop->_child, this); if (_next != NULL) _next ->verify_tree(loop->_next, parent); // Innermost loops need to verify loop bodies, // but only if no 'major_progress' int fail = 0; if (!Compile::current()->major_progress() && _child == NULL) { for( uint i = 0; i < _body.size(); i++ ) { Node *n = _body.at(i); if (n->outcnt() == 0) continue; // Ignore dead uint j; for( j = 0; j < loop->_body.size(); j++ ) if( loop->_body.at(j) == n ) break; if( j == loop->_body.size() ) { // Not found in loop body // Last ditch effort to avoid assertion: Its possible that we // have some users (so outcnt not zero) but are still dead. // Try to find from root. if (Compile::current()->root()->find(n->_idx)) { fail++; tty->print("We have that verify does not: "); n->dump(); } } } for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) { Node *n = loop->_body.at(i2); if (n->outcnt() == 0) continue; // Ignore dead uint j; for( j = 0; j < _body.size(); j++ ) if( _body.at(j) == n ) break; if( j == _body.size() ) { // Not found in loop body // Last ditch effort to avoid assertion: Its possible that we // have some users (so outcnt not zero) but are still dead. // Try to find from root. if (Compile::current()->root()->find(n->_idx)) { fail++; tty->print("Verify has that we do not: "); n->dump(); } } } assert( !fail, "loop body mismatch" ); } } #endif //------------------------------set_idom--------------------------------------- void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) { uint idx = d->_idx; if (idx >= _idom_size) { uint newsize = _idom_size<<1; while( idx >= newsize ) { newsize <<= 1; } _idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize); _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize); memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) ); _idom_size = newsize; } _idom[idx] = n; _dom_depth[idx] = dom_depth; } //------------------------------recompute_dom_depth--------------------------------------- // The dominator tree is constructed with only parent pointers. // This recomputes the depth in the tree by first tagging all // nodes as "no depth yet" marker. The next pass then runs up // the dom tree from each node marked "no depth yet", and computes // the depth on the way back down. void PhaseIdealLoop::recompute_dom_depth() { uint no_depth_marker = C->unique(); uint i; // Initialize depth to "no depth yet" for (i = 0; i < _idom_size; i++) { if (_dom_depth[i] > 0 && _idom[i] != NULL) { _dom_depth[i] = no_depth_marker; } } if (_dom_stk == NULL) { uint init_size = C->unique() / 100; // Guess that 1/100 is a reasonable initial size. if (init_size < 10) init_size = 10; _dom_stk = new GrowableArray(init_size); } // Compute new depth for each node. for (i = 0; i < _idom_size; i++) { uint j = i; // Run up the dom tree to find a node with a depth while (_dom_depth[j] == no_depth_marker) { _dom_stk->push(j); j = _idom[j]->_idx; } // Compute the depth on the way back down this tree branch uint dd = _dom_depth[j] + 1; while (_dom_stk->length() > 0) { uint j = _dom_stk->pop(); _dom_depth[j] = dd; dd++; } } } //------------------------------sort------------------------------------------- // Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the // loop tree, not the root. IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) { if( !innermost ) return loop; // New innermost loop int loop_preorder = get_preorder(loop->_head); // Cache pre-order number assert( loop_preorder, "not yet post-walked loop" ); IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer IdealLoopTree *l = *pp; // Do I go before or after 'l'? // Insert at start of list while( l ) { // Insertion sort based on pre-order if( l == loop ) return innermost; // Already on list! int l_preorder = get_preorder(l->_head); // Cache pre-order number assert( l_preorder, "not yet post-walked l" ); // Check header pre-order number to figure proper nesting if( loop_preorder > l_preorder ) break; // End of insertion // If headers tie (e.g., shared headers) check tail pre-order numbers. // Since I split shared headers, you'd think this could not happen. // BUT: I must first do the preorder numbering before I can discover I // have shared headers, so the split headers all get the same preorder // number as the RegionNode they split from. if( loop_preorder == l_preorder && get_preorder(loop->_tail) < get_preorder(l->_tail) ) break; // Also check for shared headers (same pre#) pp = &l->_parent; // Chain up list l = *pp; } // Link into list // Point predecessor to me *pp = loop; // Point me to successor IdealLoopTree *p = loop->_parent; loop->_parent = l; // Point me to successor if( p ) sort( p, innermost ); // Insert my parents into list as well return innermost; } //------------------------------build_loop_tree-------------------------------- // I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit // bits. The _nodes[] array is mapped by Node index and holds a NULL for // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the // tightest enclosing IdealLoopTree for post-walked. // // During my forward walk I do a short 1-layer lookahead to see if I can find // a loop backedge with that doesn't have any work on the backedge. This // helps me construct nested loops with shared headers better. // // Once I've done the forward recursion, I do the post-work. For each child // I check to see if there is a backedge. Backedges define a loop! I // insert an IdealLoopTree at the target of the backedge. // // During the post-work I also check to see if I have several children // belonging to different loops. If so, then this Node is a decision point // where control flow can choose to change loop nests. It is at this // decision point where I can figure out how loops are nested. At this // time I can properly order the different loop nests from my children. // Note that there may not be any backedges at the decision point! // // Since the decision point can be far removed from the backedges, I can't // order my loops at the time I discover them. Thus at the decision point // I need to inspect loop header pre-order numbers to properly nest my // loops. This means I need to sort my childrens' loops by pre-order. // The sort is of size number-of-control-children, which generally limits // it to size 2 (i.e., I just choose between my 2 target loops). void PhaseIdealLoop::build_loop_tree() { // Allocate stack of size C->unique()/2 to avoid frequent realloc GrowableArray bltstack(C->unique() >> 1); Node *n = C->root(); bltstack.push(n); int pre_order = 1; int stack_size; while ( ( stack_size = bltstack.length() ) != 0 ) { n = bltstack.top(); // Leave node on stack if ( !is_visited(n) ) { // ---- Pre-pass Work ---- // Pre-walked but not post-walked nodes need a pre_order number. set_preorder_visited( n, pre_order ); // set as visited // ---- Scan over children ---- // Scan first over control projections that lead to loop headers. // This helps us find inner-to-outer loops with shared headers better. // Scan children's children for loop headers. for ( int i = n->outcnt() - 1; i >= 0; --i ) { Node* m = n->raw_out(i); // Child if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children // Scan over children's children to find loop for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { Node* l = m->fast_out(j); if( is_visited(l) && // Been visited? !is_postvisited(l) && // But not post-visited get_preorder(l) < pre_order ) { // And smaller pre-order // Found! Scan the DFS down this path before doing other paths bltstack.push(m); break; } } } } pre_order++; } else if ( !is_postvisited(n) ) { // Note: build_loop_tree_impl() adds out edges on rare occasions, // such as com.sun.rsasign.am::a. // For non-recursive version, first, process current children. // On next iteration, check if additional children were added. for ( int k = n->outcnt() - 1; k >= 0; --k ) { Node* u = n->raw_out(k); if ( u->is_CFG() && !is_visited(u) ) { bltstack.push(u); } } if ( bltstack.length() == stack_size ) { // There were no additional children, post visit node now (void)bltstack.pop(); // Remove node from stack pre_order = build_loop_tree_impl( n, pre_order ); // Check for bailout if (C->failing()) { return; } // Check to grow _preorders[] array for the case when // build_loop_tree_impl() adds new nodes. check_grow_preorders(); } } else { (void)bltstack.pop(); // Remove post-visited node from stack } } } //------------------------------build_loop_tree_impl--------------------------- int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) { // ---- Post-pass Work ---- // Pre-walked but not post-walked nodes need a pre_order number. // Tightest enclosing loop for this Node IdealLoopTree *innermost = NULL; // For all children, see if any edge is a backedge. If so, make a loop // for it. Then find the tightest enclosing loop for the self Node. for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { Node* m = n->fast_out(i); // Child if( n == m ) continue; // Ignore control self-cycles if( !m->is_CFG() ) continue;// Ignore non-CFG edges IdealLoopTree *l; // Child's loop if( !is_postvisited(m) ) { // Child visited but not post-visited? // Found a backedge assert( get_preorder(m) < pre_order, "should be backedge" ); // Check for the RootNode, which is already a LoopNode and is allowed // to have multiple "backedges". if( m == C->root()) { // Found the root? l = _ltree_root; // Root is the outermost LoopNode } else { // Else found a nested loop // Insert a LoopNode to mark this loop. l = new IdealLoopTree(this, m, n); } // End of Else found a nested loop if( !has_loop(m) ) // If 'm' does not already have a loop set set_loop(m, l); // Set loop header to loop now } else { // Else not a nested loop if( !_nodes[m->_idx] ) continue; // Dead code has no loop l = get_loop(m); // Get previously determined loop // If successor is header of a loop (nest), move up-loop till it // is a member of some outer enclosing loop. Since there are no // shared headers (I've split them already) I only need to go up // at most 1 level. while( l && l->_head == m ) // Successor heads loop? l = l->_parent; // Move up 1 for me // If this loop is not properly parented, then this loop // has no exit path out, i.e. its an infinite loop. if( !l ) { // Make loop "reachable" from root so the CFG is reachable. Basically // insert a bogus loop exit that is never taken. 'm', the loop head, // points to 'n', one (of possibly many) fall-in paths. There may be // many backedges as well. // Here I set the loop to be the root loop. I could have, after // inserting a bogus loop exit, restarted the recursion and found my // new loop exit. This would make the infinite loop a first-class // loop and it would then get properly optimized. What's the use of // optimizing an infinite loop? l = _ltree_root; // Oops, found infinite loop if (!_verify_only) { // Insert the NeverBranch between 'm' and it's control user. NeverBranchNode *iff = new (C, 1) NeverBranchNode( m ); _igvn.register_new_node_with_optimizer(iff); set_loop(iff, l); Node *if_t = new (C, 1) CProjNode( iff, 0 ); _igvn.register_new_node_with_optimizer(if_t); set_loop(if_t, l); Node* cfg = NULL; // Find the One True Control User of m for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) { Node* x = m->fast_out(j); if (x->is_CFG() && x != m && x != iff) { cfg = x; break; } } assert(cfg != NULL, "must find the control user of m"); uint k = 0; // Probably cfg->in(0) while( cfg->in(k) != m ) k++; // But check incase cfg is a Region cfg->set_req( k, if_t ); // Now point to NeverBranch // Now create the never-taken loop exit Node *if_f = new (C, 1) CProjNode( iff, 1 ); _igvn.register_new_node_with_optimizer(if_f); set_loop(if_f, l); // Find frame ptr for Halt. Relies on the optimizer // V-N'ing. Easier and quicker than searching through // the program structure. Node *frame = new (C, 1) ParmNode( C->start(), TypeFunc::FramePtr ); _igvn.register_new_node_with_optimizer(frame); // Halt & Catch Fire Node *halt = new (C, TypeFunc::Parms) HaltNode( if_f, frame ); _igvn.register_new_node_with_optimizer(halt); set_loop(halt, l); C->root()->add_req(halt); } set_loop(C->root(), _ltree_root); } } // Weeny check for irreducible. This child was already visited (this // IS the post-work phase). Is this child's loop header post-visited // as well? If so, then I found another entry into the loop. if (!_verify_only) { while( is_postvisited(l->_head) ) { // found irreducible l->_irreducible = 1; // = true l = l->_parent; _has_irreducible_loops = true; // Check for bad CFG here to prevent crash, and bailout of compile if (l == NULL) { C->record_method_not_compilable("unhandled CFG detected during loop optimization"); return pre_order; } } } // This Node might be a decision point for loops. It is only if // it's children belong to several different loops. The sort call // does a trivial amount of work if there is only 1 child or all // children belong to the same loop. If however, the children // belong to different loops, the sort call will properly set the // _parent pointers to show how the loops nest. // // In any case, it returns the tightest enclosing loop. innermost = sort( l, innermost ); } // Def-use info will have some dead stuff; dead stuff will have no // loop decided on. // Am I a loop header? If so fix up my parent's child and next ptrs. if( innermost && innermost->_head == n ) { assert( get_loop(n) == innermost, "" ); IdealLoopTree *p = innermost->_parent; IdealLoopTree *l = innermost; while( p && l->_head == n ) { l->_next = p->_child; // Put self on parents 'next child' p->_child = l; // Make self as first child of parent l = p; // Now walk up the parent chain p = l->_parent; } } else { // Note that it is possible for a LoopNode to reach here, if the // backedge has been made unreachable (hence the LoopNode no longer // denotes a Loop, and will eventually be removed). // Record tightest enclosing loop for self. Mark as post-visited. set_loop(n, innermost); // Also record has_call flag early on if( innermost ) { if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) { // Do not count uncommon calls if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) { Node *iff = n->in(0)->in(0); if( !iff->is_If() || (n->in(0)->Opcode() == Op_IfFalse && (1.0 - iff->as_If()->_prob) >= 0.01) || (iff->as_If()->_prob >= 0.01) ) innermost->_has_call = 1; } } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) { // Disable loop optimizations if the loop has a scalar replaceable // allocation. This disabling may cause a potential performance lost // if the allocation is not eliminated for some reason. innermost->_allow_optimizations = false; innermost->_has_call = 1; // = true } } } // Flag as post-visited now set_postvisited(n); return pre_order; } //------------------------------build_loop_early------------------------------- // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. // First pass computes the earliest controlling node possible. This is the // controlling input with the deepest dominating depth. void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) { while (worklist.size() != 0) { // Use local variables nstack_top_n & nstack_top_i to cache values // on nstack's top. Node *nstack_top_n = worklist.pop(); uint nstack_top_i = 0; //while_nstack_nonempty: while (true) { // Get parent node and next input's index from stack's top. Node *n = nstack_top_n; uint i = nstack_top_i; uint cnt = n->req(); // Count of inputs if (i == 0) { // Pre-process the node. if( has_node(n) && // Have either loop or control already? !has_ctrl(n) ) { // Have loop picked out already? // During "merge_many_backedges" we fold up several nested loops // into a single loop. This makes the members of the original // loop bodies pointing to dead loops; they need to move up // to the new UNION'd larger loop. I set the _head field of these // dead loops to NULL and the _parent field points to the owning // loop. Shades of UNION-FIND algorithm. IdealLoopTree *ilt; while( !(ilt = get_loop(n))->_head ) { // Normally I would use a set_loop here. But in this one special // case, it is legal (and expected) to change what loop a Node // belongs to. _nodes.map(n->_idx, (Node*)(ilt->_parent) ); } // Remove safepoints ONLY if I've already seen I don't need one. // (the old code here would yank a 2nd safepoint after seeing a // first one, even though the 1st did not dominate in the loop body // and thus could be avoided indefinitely) if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint && is_deleteable_safept(n)) { Node *in = n->in(TypeFunc::Control); lazy_replace(n,in); // Pull safepoint now // Carry on with the recursion "as if" we are walking // only the control input if( !visited.test_set( in->_idx ) ) { worklist.push(in); // Visit this guy later, using worklist } // Get next node from nstack: // - skip n's inputs processing by setting i > cnt; // - we also will not call set_early_ctrl(n) since // has_node(n) == true (see the condition above). i = cnt + 1; } } } // if (i == 0) // Visit all inputs bool done = true; // Assume all n's inputs will be processed while (i < cnt) { Node *in = n->in(i); ++i; if (in == NULL) continue; if (in->pinned() && !in->is_CFG()) set_ctrl(in, in->in(0)); int is_visited = visited.test_set( in->_idx ); if (!has_node(in)) { // No controlling input yet? assert( !in->is_CFG(), "CFG Node with no controlling input?" ); assert( !is_visited, "visit only once" ); nstack.push(n, i); // Save parent node and next input's index. nstack_top_n = in; // Process current input now. nstack_top_i = 0; done = false; // Not all n's inputs processed. break; // continue while_nstack_nonempty; } else if (!is_visited) { // This guy has a location picked out for him, but has not yet // been visited. Happens to all CFG nodes, for instance. // Visit him using the worklist instead of recursion, to break // cycles. Since he has a location already we do not need to // find his location before proceeding with the current Node. worklist.push(in); // Visit this guy later, using worklist } } if (done) { // All of n's inputs have been processed, complete post-processing. // Compute earliest point this Node can go. // CFG, Phi, pinned nodes already know their controlling input. if (!has_node(n)) { // Record earliest legal location set_early_ctrl( n ); } if (nstack.is_empty()) { // Finished all nodes on stack. // Process next node on the worklist. break; } // Get saved parent node and next input's index. nstack_top_n = nstack.node(); nstack_top_i = nstack.index(); nstack.pop(); } } // while (true) } } //------------------------------dom_lca_internal-------------------------------- // Pair-wise LCA Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const { if( !n1 ) return n2; // Handle NULL original LCA assert( n1->is_CFG(), "" ); assert( n2->is_CFG(), "" ); // find LCA of all uses uint d1 = dom_depth(n1); uint d2 = dom_depth(n2); while (n1 != n2) { if (d1 > d2) { n1 = idom(n1); d1 = dom_depth(n1); } else if (d1 < d2) { n2 = idom(n2); d2 = dom_depth(n2); } else { // Here d1 == d2. Due to edits of the dominator-tree, sections // of the tree might have the same depth. These sections have // to be searched more carefully. // Scan up all the n1's with equal depth, looking for n2. Node *t1 = idom(n1); while (dom_depth(t1) == d1) { if (t1 == n2) return n2; t1 = idom(t1); } // Scan up all the n2's with equal depth, looking for n1. Node *t2 = idom(n2); while (dom_depth(t2) == d2) { if (t2 == n1) return n1; t2 = idom(t2); } // Move up to a new dominator-depth value as well as up the dom-tree. n1 = t1; n2 = t2; d1 = dom_depth(n1); d2 = dom_depth(n2); } } return n1; } //------------------------------compute_idom----------------------------------- // Locally compute IDOM using dom_lca call. Correct only if the incoming // IDOMs are correct. Node *PhaseIdealLoop::compute_idom( Node *region ) const { assert( region->is_Region(), "" ); Node *LCA = NULL; for( uint i = 1; i < region->req(); i++ ) { if( region->in(i) != C->top() ) LCA = dom_lca( LCA, region->in(i) ); } return LCA; } bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) { bool had_error = false; #ifdef ASSERT if (early != C->root()) { // Make sure that there's a dominance path from use to LCA Node* d = use; while (d != LCA) { d = idom(d); if (d == C->root()) { tty->print_cr("*** Use %d isn't dominated by def %s", use->_idx, n->_idx); n->dump(); use->dump(); had_error = true; break; } } } #endif return had_error; } Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) { // Compute LCA over list of uses bool had_error = false; Node *LCA = NULL; for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) { Node* c = n->fast_out(i); if (_nodes[c->_idx] == NULL) continue; // Skip the occasional dead node if( c->is_Phi() ) { // For Phis, we must land above on the path for( uint j=1; jreq(); j++ ) {// For all inputs if( c->in(j) == n ) { // Found matching input? Node *use = c->in(0)->in(j); if (_verify_only && use->is_top()) continue; LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error; } } } else { // For CFG data-users, use is in the block just prior Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0); LCA = dom_lca_for_get_late_ctrl( LCA, use, n ); if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error; } } assert(!had_error, "bad dominance"); return LCA; } //------------------------------get_late_ctrl---------------------------------- // Compute latest legal control. Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) { assert(early != NULL, "early control should not be NULL"); Node* LCA = compute_lca_of_uses(n, early); #ifdef ASSERT if (LCA == C->root() && LCA != early) { // def doesn't dominate uses so print some useful debugging output compute_lca_of_uses(n, early, true); } #endif // if this is a load, check for anti-dependent stores // We use a conservative algorithm to identify potential interfering // instructions and for rescheduling the load. The users of the memory // input of this load are examined. Any use which is not a load and is // dominated by early is considered a potentially interfering store. // This can produce false positives. if (n->is_Load() && LCA != early) { Node_List worklist; Node *mem = n->in(MemNode::Memory); for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) { Node* s = mem->fast_out(i); worklist.push(s); } while(worklist.size() != 0 && LCA != early) { Node* s = worklist.pop(); if (s->is_Load()) { continue; } else if (s->is_MergeMem()) { for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) { Node* s1 = s->fast_out(i); worklist.push(s1); } } else { Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0); assert(sctrl != NULL || s->outcnt() == 0, "must have control"); if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) { LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n); } } } } assert(LCA == find_non_split_ctrl(LCA), "unexpected late control"); return LCA; } // true if CFG node d dominates CFG node n bool PhaseIdealLoop::is_dominator(Node *d, Node *n) { if (d == n) return true; assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes"); uint dd = dom_depth(d); while (dom_depth(n) >= dd) { if (n == d) return true; n = idom(n); } return false; } //------------------------------dom_lca_for_get_late_ctrl_internal------------- // Pair-wise LCA with tags. // Tag each index with the node 'tag' currently being processed // before advancing up the dominator chain using idom(). // Later calls that find a match to 'tag' know that this path has already // been considered in the current LCA (which is input 'n1' by convention). // Since get_late_ctrl() is only called once for each node, the tag array // does not need to be cleared between calls to get_late_ctrl(). // Algorithm trades a larger constant factor for better asymptotic behavior // Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) { uint d1 = dom_depth(n1); uint d2 = dom_depth(n2); do { if (d1 > d2) { // current lca is deeper than n2 _dom_lca_tags.map(n1->_idx, tag); n1 = idom(n1); d1 = dom_depth(n1); } else if (d1 < d2) { // n2 is deeper than current lca Node *memo = _dom_lca_tags[n2->_idx]; if( memo == tag ) { return n1; // Return the current LCA } _dom_lca_tags.map(n2->_idx, tag); n2 = idom(n2); d2 = dom_depth(n2); } else { // Here d1 == d2. Due to edits of the dominator-tree, sections // of the tree might have the same depth. These sections have // to be searched more carefully. // Scan up all the n1's with equal depth, looking for n2. _dom_lca_tags.map(n1->_idx, tag); Node *t1 = idom(n1); while (dom_depth(t1) == d1) { if (t1 == n2) return n2; _dom_lca_tags.map(t1->_idx, tag); t1 = idom(t1); } // Scan up all the n2's with equal depth, looking for n1. _dom_lca_tags.map(n2->_idx, tag); Node *t2 = idom(n2); while (dom_depth(t2) == d2) { if (t2 == n1) return n1; _dom_lca_tags.map(t2->_idx, tag); t2 = idom(t2); } // Move up to a new dominator-depth value as well as up the dom-tree. n1 = t1; n2 = t2; d1 = dom_depth(n1); d2 = dom_depth(n2); } } while (n1 != n2); return n1; } //------------------------------init_dom_lca_tags------------------------------ // Tag could be a node's integer index, 32bits instead of 64bits in some cases // Intended use does not involve any growth for the array, so it could // be of fixed size. void PhaseIdealLoop::init_dom_lca_tags() { uint limit = C->unique() + 1; _dom_lca_tags.map( limit, NULL ); #ifdef ASSERT for( uint i = 0; i < limit; ++i ) { assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); } #endif // ASSERT } //------------------------------clear_dom_lca_tags------------------------------ // Tag could be a node's integer index, 32bits instead of 64bits in some cases // Intended use does not involve any growth for the array, so it could // be of fixed size. void PhaseIdealLoop::clear_dom_lca_tags() { uint limit = C->unique() + 1; _dom_lca_tags.map( limit, NULL ); _dom_lca_tags.clear(); #ifdef ASSERT for( uint i = 0; i < limit; ++i ) { assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer"); } #endif // ASSERT } //------------------------------build_loop_late-------------------------------- // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. // Second pass finds latest legal placement, and ideal loop placement. void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) { while (worklist.size() != 0) { Node *n = worklist.pop(); // Only visit once if (visited.test_set(n->_idx)) continue; uint cnt = n->outcnt(); uint i = 0; while (true) { assert( _nodes[n->_idx], "no dead nodes" ); // Visit all children if (i < cnt) { Node* use = n->raw_out(i); ++i; // Check for dead uses. Aggressively prune such junk. It might be // dead in the global sense, but still have local uses so I cannot // easily call 'remove_dead_node'. if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead? // Due to cycles, we might not hit the same fixed point in the verify // pass as we do in the regular pass. Instead, visit such phis as // simple uses of the loop head. if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) { if( !visited.test(use->_idx) ) worklist.push(use); } else if( !visited.test_set(use->_idx) ) { nstack.push(n, i); // Save parent and next use's index. n = use; // Process all children of current use. cnt = use->outcnt(); i = 0; } } else { // Do not visit around the backedge of loops via data edges. // push dead code onto a worklist _deadlist.push(use); } } else { // All of n's children have been processed, complete post-processing. build_loop_late_post(n); if (nstack.is_empty()) { // Finished all nodes on stack. // Process next node on the worklist. break; } // Get saved parent node and next use's index. Visit the rest of uses. n = nstack.node(); cnt = n->outcnt(); i = nstack.index(); nstack.pop(); } } } } //------------------------------build_loop_late_post--------------------------- // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping. // Second pass finds latest legal placement, and ideal loop placement. void PhaseIdealLoop::build_loop_late_post( Node *n ) { if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) { _igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops. } // CFG and pinned nodes already handled if( n->in(0) ) { if( n->in(0)->is_top() ) return; // Dead? // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads // _must_ be pinned (they have to observe their control edge of course). // Unlike Stores (which modify an unallocable resource, the memory // state), Mods/Loads can float around. So free them up. bool pinned = true; switch( n->Opcode() ) { case Op_DivI: case Op_DivF: case Op_DivD: case Op_ModI: case Op_ModF: case Op_ModD: case Op_LoadB: // Same with Loads; they can sink case Op_LoadUS: // during loop optimizations. case Op_LoadD: case Op_LoadF: case Op_LoadI: case Op_LoadKlass: case Op_LoadNKlass: case Op_LoadL: case Op_LoadS: case Op_LoadP: case Op_LoadN: case Op_LoadRange: case Op_LoadD_unaligned: case Op_LoadL_unaligned: case Op_StrComp: // Does a bunch of load-like effects case Op_StrEquals: case Op_StrIndexOf: case Op_AryEq: pinned = false; } if( pinned ) { IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n)); if( !chosen_loop->_child ) // Inner loop? chosen_loop->_body.push(n); // Collect inner loops return; } } else { // No slot zero if( n->is_CFG() ) { // CFG with no slot 0 is dead _nodes.map(n->_idx,0); // No block setting, it's globally dead return; } assert(!n->is_CFG() || n->outcnt() == 0, ""); } // Do I have a "safe range" I can select over? Node *early = get_ctrl(n);// Early location already computed // Compute latest point this Node can go Node *LCA = get_late_ctrl( n, early ); // LCA is NULL due to uses being dead if( LCA == NULL ) { #ifdef ASSERT for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) { assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead"); } #endif _nodes.map(n->_idx, 0); // This node is useless _deadlist.push(n); return; } assert(LCA != NULL && !LCA->is_top(), "no dead nodes"); Node *legal = LCA; // Walk 'legal' up the IDOM chain Node *least = legal; // Best legal position so far while( early != legal ) { // While not at earliest legal #ifdef ASSERT if (legal->is_Start() && !early->is_Root()) { // Bad graph. Print idom path and fail. tty->print_cr( "Bad graph detected in build_loop_late"); tty->print("n: ");n->dump(); tty->cr(); tty->print("early: ");early->dump(); tty->cr(); int ct = 0; Node *dbg_legal = LCA; while(!dbg_legal->is_Start() && ct < 100) { tty->print("idom[%d] ",ct); dbg_legal->dump(); tty->cr(); ct++; dbg_legal = idom(dbg_legal); } assert(false, "Bad graph detected in build_loop_late"); } #endif // Find least loop nesting depth legal = idom(legal); // Bump up the IDOM tree // Check for lower nesting depth if( get_loop(legal)->_nest < get_loop(least)->_nest ) least = legal; } assert(early == legal || legal != C->root(), "bad dominance of inputs"); // Try not to place code on a loop entry projection // which can inhibit range check elimination. if (least != early) { Node* ctrl_out = least->unique_ctrl_out(); if (ctrl_out && ctrl_out->is_CountedLoop() && least == ctrl_out->in(LoopNode::EntryControl)) { Node* least_dom = idom(least); if (get_loop(least_dom)->is_member(get_loop(least))) { least = least_dom; } } } #ifdef ASSERT // If verifying, verify that 'verify_me' has a legal location // and choose it as our location. if( _verify_me ) { Node *v_ctrl = _verify_me->get_ctrl_no_update(n); Node *legal = LCA; while( early != legal ) { // While not at earliest legal if( legal == v_ctrl ) break; // Check for prior good location legal = idom(legal) ;// Bump up the IDOM tree } // Check for prior good location if( legal == v_ctrl ) least = legal; // Keep prior if found } #endif // Assign discovered "here or above" point least = find_non_split_ctrl(least); set_ctrl(n, least); // Collect inner loop bodies IdealLoopTree *chosen_loop = get_loop(least); if( !chosen_loop->_child ) // Inner loop? chosen_loop->_body.push(n);// Collect inner loops } #ifndef PRODUCT //------------------------------dump------------------------------------------- void PhaseIdealLoop::dump( ) const { ResourceMark rm; Arena* arena = Thread::current()->resource_area(); Node_Stack stack(arena, C->unique() >> 2); Node_List rpo_list; VectorSet visited(arena); visited.set(C->top()->_idx); rpo( C->root(), stack, visited, rpo_list ); // Dump root loop indexed by last element in PO order dump( _ltree_root, rpo_list.size(), rpo_list ); } void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const { loop->dump_head(); // Now scan for CFG nodes in the same loop for( uint j=idx; j > 0; j-- ) { Node *n = rpo_list[j-1]; if( !_nodes[n->_idx] ) // Skip dead nodes continue; if( get_loop(n) != loop ) { // Wrong loop nest if( get_loop(n)->_head == n && // Found nested loop? get_loop(n)->_parent == loop ) dump(get_loop(n),rpo_list.size(),rpo_list); // Print it nested-ly continue; } // Dump controlling node for( uint x = 0; x < loop->_nest; x++ ) tty->print(" "); tty->print("C"); if( n == C->root() ) { n->dump(); } else { Node* cached_idom = idom_no_update(n); Node *computed_idom = n->in(0); if( n->is_Region() ) { computed_idom = compute_idom(n); // computed_idom() will return n->in(0) when idom(n) is an IfNode (or // any MultiBranch ctrl node), so apply a similar transform to // the cached idom returned from idom_no_update. cached_idom = find_non_split_ctrl(cached_idom); } tty->print(" ID:%d",computed_idom->_idx); n->dump(); if( cached_idom != computed_idom ) { tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d", computed_idom->_idx, cached_idom->_idx); } } // Dump nodes it controls for( uint k = 0; k < _nodes.Size(); k++ ) { // (k < C->unique() && get_ctrl(find(k)) == n) if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) { Node *m = C->root()->find(k); if( m && m->outcnt() > 0 ) { if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) { tty->print_cr("*** BROKEN CTRL ACCESSOR! _nodes[k] is %p, ctrl is %p", _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL); } for( uint j = 0; j < loop->_nest; j++ ) tty->print(" "); tty->print(" "); m->dump(); } } } } } // Collect a R-P-O for the whole CFG. // Result list is in post-order (scan backwards for RPO) void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const { stk.push(start, 0); visited.set(start->_idx); while (stk.is_nonempty()) { Node* m = stk.node(); uint idx = stk.index(); if (idx < m->outcnt()) { stk.set_index(idx + 1); Node* n = m->raw_out(idx); if (n->is_CFG() && !visited.test_set(n->_idx)) { stk.push(n, 0); } } else { rpo_list.push(m); stk.pop(); } } } #endif //============================================================================= //------------------------------LoopTreeIterator----------------------------------- // Advance to next loop tree using a preorder, left-to-right traversal. void LoopTreeIterator::next() { assert(!done(), "must not be done."); if (_curnt->_child != NULL) { _curnt = _curnt->_child; } else if (_curnt->_next != NULL) { _curnt = _curnt->_next; } else { while (_curnt != _root && _curnt->_next == NULL) { _curnt = _curnt->_parent; } if (_curnt == _root) { _curnt = NULL; assert(done(), "must be done."); } else { assert(_curnt->_next != NULL, "must be more to do"); _curnt = _curnt->_next; } } }